1. Field of the Invention
This invention relates to a planetary gear device, more particularly to a planetary gear device for reducing speed of an output shaft of a motor.
2. Description of the Related Art
Referring to FIG. 1, a conventional planetary gear device is shown to include a mounting frame 2, and an adapter frame 3 which is secured to the mounting frame 2. A planet carrier 4 includes an output shaft 404 which is rotatably mounted in the mounting frame 2 via a first bearing member 401 and which extends outwardly to transmit rotary movement of reduced speed to a load, and a carrying frame member 405 which is surrounded by an inner annular toothed portion 201 of the mounting frame 2 and which is rotatably mounted in the mounting frame 2 via a second bearing member 402. A plurality of planet wheel members 406 are rotatably mounted on the carrying frame member 405, and mesh with the inner annular tooth portion 201. A force transmitting member 5 includes a sun wheel member 501 which meshes with the planet wheel members 406, and a coupling tubular member 502 with an outer circumferential wall surface which confronts an inner peripheral wall surface of the adapter frame 3 to couple with and to be driven by an output shaft (not shown) of a motor. A third bearing member 6 includes outer and inner annular races 601,602, and is interposed between the inner peripheral wall surface and the coupling tubular member 502 to rotatably support the coupling tubular member 502 relative to the adapter frame 3. A pair of oil seal members 403,603 are disposed to confine a lubricating oil passage for the bearing members 401,402,6, the inner annular tooth portion 201, planet wheel members 406 and the sun wheel member 501. However, misalignment of the sun wheel member 501 with the planet carrier 4 easily results after assembly of the mounting and adapter frames 2,3, and will arise large noise and vibration between the sun wheel member 501 and the planet wheel members 406 during the force transmitting operation.
To solve the above problem, referring to FIG. 2, another conventional planetary gear device, such as that disclosed in U.S. Pat. No. 5,687,480, is shown to include a deformable O-ring 301xe2x80x2 disposed between an inner peripheral wall surface of an adapter frame 3xe2x80x2 and a bearing member 6xe2x80x2. As such, a tolerance connection is maintained between a sun wheel member 5xe2x80x2 and a mounting frame 2xe2x80x2 for accurate meshing between the sun wheel member 5xe2x80x2 and planet wheel members 406xe2x80x2. However, the misalignment of the sun wheel member 5xe2x80x2 with a planet carrier (not shown) can still occur due to fatigue and wearing of the O-ring 301xe2x80x2 after a long-term use.
The object of the present invention is to provide a planetary gear device which can overcome the aforesaid drawbacks of the prior art.
According to this invention, the planetary gear device includes a mounting frame with an inner annular wall surface which surrounds a first axis and which extends in an axial direction parallel to the first axis to confine an accommodation chamber. The inner annular wall surface includes proximate and distal annular segments opposite to each other in the axial direction, and an intermediate annular segment which is interposed therebetween and which has an inner annular toothed portion. A planet carrier includes an output shaft which is rotatably mounted on the distal annular segment about the first axis via a first bearing member and which extends outwardly of the accommodation chamber so as to be adapted to transmit rotary movement of reduced speed to a load, and a carrying frame member with mounting and coupling frame portions. The mounting frame portion extends from the output shaft in the axial direction, and is surrounded by the inner annular toothed portion. The coupling frame portion extends from the mounting frame portion in the axial direction, and has inner and outer coupling annular wall surfaces opposite to each other in a radial direction relative to the axial direction. The outer coupling annular wall surface is rotatably mounted on the proximate annular segment via a second bearing member. A plurality of planet wheel members are angularly displaced from one another, and are rotatably mounted on the mounting frame portion about a plurality of second axes which are parallel to the first axis such that each of the planet wheel members meshes with the inner annular toothed portion. A force transmitting member includes a sun wheel member which extends along the first axis and which meshes with the planet wheel members, and a coupling tubular member with a circumferential mounting portion and a tubular coupling portion. The circumferential mounting portion extends from the sun wheel member in the axial direction, and has an outer circumferential wall surface which confronts and which is rotatably mounted on the inner coupling annular wall surface via a third bearing member. The tubular coupling portion extends from the circumferential mounting portion in the axial direction and outwardly of the coupling frame portion so as to be adapted to couple with and be driven by an output shaft of a motor.